1. Field of the Invention
The present invention related generally to a magnetic tape cartridge for use as a data storage medium. More specifically, the invention relates to a magnetic tape cartridge compatible with a disk drive and being particularly useful as back-up storage media for a computer and so forth which utilize magnetic disks. Further particularly, the invention relates to a magnetic tape cartridge incorporating a tape guide for accurately positioning a magnetic tape with respect to a disk drive head for enabling transfer of data between the magnetic tape and the disk drive head.
2. Description of the Background Art
Various magnetic disks and disk drives designed for use with associated disks have been developed and proposed for storing data. For example, the U.S. Pat. No. 4,445,155, issued on Apr. 24, 1984, to Takahashi et al, discloses one of typical constructions of a microfloppy disk, i.e. 3.5-inch floppy disk and disk drive therefor. The floppy disk is in a form of a floppy disk cassette or cartridge generally comprising a flexible magnetic disk and a cassette or cartridge casing. The flexible disk includes a center core disk designed to be chucked on a turntable of the disk drive. The disk drive drives the flexible disk and the center core disk to rotate.
Such floppy disks are useful for fast access. On the other hand, the floppy disks have limited data storage capacity. Archival or backup storage data stored on a hard disk generally takes 20 to 80 floppy disks due to their large capacity. This involves substantial expense for the user.
Magnetic tapes have conventionally been used as data storage medium. The magnetic tapes have much larger storage capacity than the floppy disk. On the other hand, the magnetic tapes are considered to be inconvenient when fast access for data is required. In other words, when fast access is not required, the magnetic tapes should be useful because of larger storage capacity. Therefore, as a backup storage for a hard disk, the magnetic tapes should be regarded as a useful and convenient medium to use.
As is well known, in order to perform recording and reproducing on magnetic tapes, a so-called "data recorder" which is a sort of magnetic tape recording and reproducing apparatus is needed. Whereas, recording and reproduction of data on the magnetic disks is performed by means of a disk drive. Consequently, in order to take the magnetic tapes as backup storage medium, both of data recorder and disk drive are required for copying data from the hard disk onto the magnetic tape storage medium. This is an additional expense for the users.
So as to allow the user to utilize magnetic tape for inexpensive backup storage of data on hard disks, or floppy disks, it would be beneficial to provide a magnetic tape cartridge compatible with floppy disk drives so that it may be driven by the same drive unit. For this purpose, there has been proposed a novel and useful disk-drive-compatible magnetic tape cartridge in the U.S. patent application Ser. No. 713,162, filed on Mar. 18, 1985. The same invention has been disclosed in the Japanese Patent First Publication (Tokkai) Showa 61-214188, published on Sept. 24, 1986. The proposed magnetic tape cartridge can utilize the read/write head or heads of a disk drive to write data and/or read data from the magnetic tape. The magnetic tape cartridge contains a tape media for data storage, a mechanism to register the tape with respect to a location, at which data is written to the tape or is read from the tape by the read/write head or heads of the disk drive, a mechanism for storing the tape media, and a mechanism to feed the tape past the read/write head or heads. The magnetic tape cartridge has a portion having an external shape and size which allow that portion to be inserted into the disk drive to enable the tape to be placed in the vicinity of the read/write head or heads.
The Henze's magnetic tape cartridge is successful in making the magnetic tape applicable -for the disk drive. However, there has arisen a difficulty in attempting to achieve high-density recording on the magnetic tape. This comes from difficulty in accurately positioning the magnetic tape with respect to the disk drive head. Namely, in the usual 3.5-inch floppy disk, such as that disclosed in Takahashi et al, is concerned, the magnetic disk is precisely co-axially formed with a center core disk. Therefore, by chucking the center core disk onto a turntable of a disk drive, the floppy disk can be accurately positioned with respect to the disk drive head. Therefore, recording tracks on the floppy disk can be precisely positioned at respectively predetermined positions for accurate tracking of the disk drive head. A mechanism to ensure that the tape is accurately registered with the read/write heads of the disk drive is disclosed in the U.S. patent application Ser. No. 713,162, filed Mar. 18, 1985. As disclosed in such application, guide pins are provided within the tape cartridge to accurately guide and locate the tape within the tape cartridge. The tape cartridge itself is aligned or registered with respect to the read/write heads of the disk drive accurately positioning the tape cartridge with respect to the disk drive in reference to three points. The microfloppy disk cassette normally used has a pair of holes in its protective shell. These holes fit over a pair of pins in the disk drive for accurately positioning the floppy disk with respect to the disk drive. The tape cartridge also includes a pair of holes which are positioned to fit over the pair of pins in the disk drive unit; these provide two of the three points of reference. The remaining point of reference is provided by a tight clearance fit between a circular hole at the center of the hub of a center core assembly in the tape cartridge to the disk drive spindle motor's circular shaft.